Appbar actions are not accessible

### Current behaviour
When using a screen leader like iOS VoiceOver the `Appbar.Header` component is passed the prop `accessible={true}`, which groups its children into a single selectable component. This makes it so that a user using VoiceOver is not able to focus on the individual actions in the Appbar (ex: "Back" or "Close")

### Expected behaviour
The Appbar should allow for each of it's child components to be actionable via screen reader.

### How to reproduce?
Try navigating to any of the actions in this example component using a screenreader:
```

{}} />

{}} accessibilityLabel="Search"/>
{}} accessibilityLabel="More"/>

```

### What have you tried so far?
I've tried explicitly passing the Appbar `accessible={false}`, making child View components accessible, and creating a patch that sets the `Appbar` accessibility to false

### Your Environment

| software | version
| --------------------- | -------
| ios | 18.0
| android | x
| react-native | 0.73.6
| react-native-paper | ^5.8.0
| node | 20.11.1
| npm or yarn | 1.22.22
| expo sdk | ^50.0.17